Method and system for manufacturing a cylinder head

ABSTRACT

A method and system for machining a cylinder head include loading a cylinder head into a first five axis computer numerically controlled (CNC) machine. A first fixture of the first CNC machine is then located against a top surface of the cylinder head such that the cylinder head is in a horizontal position. The first CNC machine then machines the cylinder head in the horizontal position. A second fixture of the first CNC machine is then located against a bottom surface of the cylinder head such that the cylinder head is in a vertical position. The first CNC machine then machines the cylinder head in the vertical position. The cylinder head is then moved into a second five axis CNC machine. A fixture of the second CNC machine is then located against a bottom surface of the cylinder head. The second CNC machine then machines the cylinder head.

TECHNICAL FIELD

[0001] The present invention generally relates to cylinder headmanufacturing methods and systems and, more particularly, to a methodand system for machining a cylinder head using a pair of five axiscomputerized numerical control (CNC) machines in three machining setups.

BACKGROUND ART

[0002] Typically, cylinder heads are machined in eight to twenty or moremachining setups. A problem associated with so many machining setups ispart variability and system inefficiencies incurred by stringingmachines out serially as opposed to a parallel system. What is needed isa method for machining cylinder heads in less machining setups using aminimal amount of CNC machines.

DISCLOSURE OF INVENTION

[0003] Accordingly, it is an object of the present invention to providea method for machining a cylinder head using a pair of five axiscomputerized numerical control (CNC) machines in three or less machiningsetups.

[0004] In accordance with the above object and other objects, thepresent invention provides a method and system for machining a cylinderhead. The method and system include loading a cylinder head into a firstfive axis computer numerically controlled (CNC) machine. A first fixtureof the first CNC machine is then located against a top surface of thecylinder head such that the cylinder head is in a horizontal position.The first CNC machine then machines the cylinder head in the horizontalposition. A second fixture of the first CNC machine is then locatedagainst a bottom surface of the cylinder head such that the cylinderhead is in a vertical position. The first CNC machine then machines thecylinder head in the vertical position. The cylinder head is then movedinto a second five axis CNC machine. A fixture of the second CNC machineis then located against a bottom surface of the cylinder head. Thesecond CNC machine then machines the cylinder head.

[0005] Preferably, the first fixture of the first CNC machine is locatedagainst a top surface of the cylinder head with respect to cylinder headcast locators and combustion chamber buttons of the cylinder head. Thesecond fixture of the first CNC machine is located against a bottomsurface of the cylinder head with respect to manufacturing holes of thecylinder head.

[0006] Preferably, the first CNC machine machines the cylinder head inthe horizontal position by orienting a spindle of the first CNC machineadjacent the bottom surface of the cylinder head to machine the bottomsurface of the cylinder head with the spindle as a function of depth ofthe combustion chamber buttons of the cylinder head.

BRIEF DESCRIPTION OF DRAWINGS

[0007] The present invention will now be described in further detailand, by way of example, with reference to the accompanying drawings, inwhich:

[0008]FIG. 1 illustrates a schematic cross-sectional view of an exampleof an engine assembly having a cylinder head machined in accordance withthe method and system of the present invention;

[0009]FIG. 2 illustrates a bottom view of a cylinder head to be machinedin accordance with the method and system of the present invention;

[0010]FIG. 3 illustrates a top view of the cylinder head shown in FIG.2;

[0011]FIG. 4 illustrates a block diagram describing overall operation ofthe method and system of the present invention;

[0012]FIG. 5 illustrates the configuration of a five axis CNC machinefor the first and second machining setups; and

[0013]FIG. 6 illustrates the configuration of the five axis CNC machinefor the third and final machining setup.

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] Referring now to FIG. 1, a schematic cross-sectional view of anexemplary engine assembly 10 having a cylinder head 12 machined inaccordance with the method and system of the present invention is shown.It is to be noted that cylinder head 12 is just one example of the manydifferent types of cylinder heads that may be machined in accordancewith the present invention. General examples of such cylinder headsinclude those for two and four cycle engines, those having overheadcamshafts and camshafts located in the cylinder block, those having pushrod configuration, and the like. Cylinder head 12 mounts to a cylinderblock 14 via a cylinder head gasket 15. Cylinder head 12 includes anintake face 16 having intake ports and an exhaust face 18 having exhaustports. Cylinder head 12 further includes a plurality of intake valves 20and exhaust valves 22 each associated with a respective top cylindercombustion chamber section 24 of the cylinder head. Intake valves 20 andexhaust valves 22 are movable within respective top cylinder combustionchamber sections 24 of cylinder head 12. Intake and exhaust ports leadfrom top cylinder combustion chamber sections 24 to the intake andexhaust manifolds. The ends of the intake and exhaust ports that entertop cylinder combustion chamber sections 24 contain respective valveseats 28. Additionally, valve guides 29 which help align valves 20,22are machined into cylinder head 12.

[0015] Top cylinder combustion chamber sections 24 of cylinder head 12are positioned over corresponding bottom cylinder bores 26 of cylinderblock 14. A piston 30 fits into each bottom cylinder bore 26. Aconnecting rod 32 connects piston 30 to a crankshaft 34. Piston 30 inconjunction with other pistons of engine assembly 10 moves up and downin cylinder bore 26 to rotate crankshaft 34. Preferably, engine assembly10 includes a number of cylinder/piston assemblies which are configuredfor conventional four cycle operation. The rotation of crankshaft 34provides driving power from engine assembly 10 to move a vehicle.

[0016] Cylinder head 12 includes a valve train for opening and closingvalves 20,22. The valve train may include a camshaft 36, or have a pushrod rocker configuration, operable for opening and closing intake valves20 and a camshaft 38 operable for opening and closing exhaust valves 22.Both camshafts 36, 38 have cam lobes 37, 39 which contact valve springand bucket tappet assemblies 40, 42 to move valves 20,22 up and down forclosing and opening access between ports 16, 18 and combustion chambers24, 26. Camshafts 36, 38 are housed within respective cam towers 44, 46of cylinder head 12. Cylinder head 12 further includes a spark plug 48for providing a spark in combustion chambers 24,26.

[0017] Referring now to FIGS. 2 and 3, with continual reference to FIG.1, respective bottom and top views of cylinder head 12 are shown.Cylinder head 12 includes a bottom surface 52 (joint face) whichattaches to cylinder block 14 via head gasket 15 and cylinder headbolts. Cylinder head 12 includes a top surface 54 (rocker cover railside) having a plurality of cam towers 56. Intake face 16 has an intakeport 58 associated with each combustion chamber 24. Similarly, exhaustface 18 has an exhaust port 60 associated with each combustion chamber24. Cylinder head 12 has a front face 62 and a rear face 64.

[0018] Cylinder head 12 includes a plurality of fastener apertures 66for bolting the cylinder head to cylinder block 14. Cylinder head 12further includes a pair of manufacturing holes 68,70. Camshaft 38extends through cylinder head 12 along a camshaft bore 72. Cylinder head12 further includes “Y”, “X”, and “Z” cast locators (one “Z”, two “Y”and three “X” cast locators) for orienting the cylinder head in a fiveaxis CNC machine. Cylinder head 12 also includes oil holes 71 forenabling oil to lubricate the running parts of the cylinder head.

[0019] Referring now to FIG. 4, a block diagram 80 describing overalloperation of the method and system of the present invention is shown.Block diagram 80 describes a series of operations (OP) for machiningcylinder head 12 in accordance with the present invention. In general,the series of operations include performing three machining setups in afive axis CNC machine for machining a cylinder head. Preferably, thefirst two machining setups are performed in a first five axis CNCmachine and the third and final machining setup is performed in a secondfive axis CNC machine. Alternatively, all three machining setups areperformed in the first CNC machine.

[0020] Initially, a plurality of cylinder head castings are each loadedinto respective five axis computer numerically controlled (CNC) machinesas shown in block 82. Each of the parallel arranged five axis CNCmachine are used to perform the same operations on respective cylinderhead castings as shown in blocks 84. Accordingly, only machiningoperations (OP-10 and OP-20) of one of the five axis CNC machines on acylinder head casting will be described further in detail below.

[0021] Referring now to FIG. 5, with continual reference to FIGS. 1-4, aconfiguration of a five axis CNC machine 100 for performing first andsecond machining operations OP-10 and OP-20 shown in block 84 is shown.CNC machine 100 includes a five dimensional motion system includingthree rigid carriages for three coordinate axis (X, Y, Z) translationalmovement, a fourth axis rotating for A-axis rotation, and a fifth axisfor B-axis tilt.

[0022] CNC machine 100 includes two pallets (not shown). One palletholds two cylinder heads for first and second machining operations OP-10and OP-20 and the other pallet acts as a station for unloading andloading cylinder heads. CNC machine 100 generally operates in accordancewith a description of the cylinder head and parameters for machining thecylinder head with a spindle. CNC machine 100 moves cylinder head 12along a three dimensional path while machining the cylinder head withthe spindle in accordance with the desired parameters.

[0023] CNC machine 100 includes a machine table 101, a tombstone 102,and a pair of fixtures 104 and 106. Tombstone 102 and fixtures 104 and106 hold cylinder head 12 in CNC machine 100 for performing machining ofthe cylinder head in accordance with first and second machiningoperations OP-10 and OP-20.

[0024] CNC machine 100 first performs first machining operation OP-10 oncylinder head 12. To do so, fixture 106 locates off of “Y” and “Z” castlocators on cylinder head 12. Fixture 106 holds cylinder head 12 in ahorizontal (or vertical) position and top surface 54 of the cylinderhead clamps up against a rocker cover. CNC machine 100 then probes thethree “X” cast locators and orients bottom surface 52 of cylinder head12 perpendicular to the spindle of the CNC machine. Then CNC machine 100probes combustion chamber buttons 25 each within respective top cylindercombustion chamber sections 24 for face depth. During the probingoperation CNC machine 100 rotates cylinder head 12 to equalizecombustion chamber button depth. CNC machine 100 then orients cylinderhead 12 to machine bottom surface 52 as a function of the face depth oftop cylinder combustion chamber sections 24 and then mills the bottomsurface (joint face). CNC machine 100 then drills all fastener apertures66, finish reams manufacturing holes 68, 70, and drills and taps oilholes 71.

[0025] CNC machine 100 then rolls cylinder head 12 to a desired anglefor finishing intake and exhaust valves 16, 18 parent metal work.Machine table 101 is then indexed by 90 degrees to perform milling,drilling, and tapping procedures on front thrust face 62 and the camthrust face. Machine table 101 is then indexed by 180 degrees to performmilling, drilling, and tapping procedures on rear thrust face 64 and thecam thrust face.

[0026] CNC machine 100 then performs second machining operation OP-20 oncylinder head 12. To do so, fixture 104 locates off of manufacturingholes 68, 70 and bottom surface 52 of cylinder head 12 and clamps upagainst the bottom surface to hold the cylinder head in a vertical (orhorizontal) position such that top surface 54 is oriented towards thespindle of the CNC machine. CNC machine 100 then finishes rocker coverrails, semi finishes cam ½ rounds, mills cam towers 56, and then drills,taps, and reams the dowels of cylinder head 12. CNC machine 100 thenspot face fastener apertures 66, finishes cam oil feeds, hydraulic lashadjusters, spring seats, and spark plug holes, and drills cam shaft oilpassages. Machine table 101 is then indexed by 90 degrees to performmilling, drilling, and tapping procedures on exhaust face 18. Machinetable 101 is then indexed by 180 degrees to perform milling, drilling,and tapping procedures on intake face 16.

[0027] As shown in FIG. 4, after the five axis CNC machine 100 performsthe first and second machining operations OP-10 and OP-20 on cylinderhead 12 the cylinder head is then removed from the five axis CNC machineand washed as shown in operations Op-30 block 86. The oil galleys andwater passages of cylinder head 12 are then leaked tested as shown inoperations OP-40 block 88. The valve guides, valve seats, and cam capsare installed in cylinder head 12 as shown in operations OP-50 block 90.

[0028] Cylinder head 12 is then moved into a second five axis CNCmachine 120 as shown in operations OP-60 block 92 for a third and finalround of machining. CNC machine 120 is identical to CNC machine 100.Accordingly, cylinder head 12 could be moved back into CNC machine 100for the third round of machining. However, it is envisioned that duringmanufacturing CNC machine 100 will perform the second round of machiningon a new cylinder head while CNC machine 120 performs the third round ofmachining on cylinder head 12.

[0029] Referring now to FIG. 6, with continual reference to FIGS. 1through 5, CNC machine 120 performs the third round of machining oncylinder head 12 by initially locating fixture 108 off of manufacturingholes 68,70 and bottom surface 52 of cylinder head 12 and clamps upagainst the bottom surface. CNC machine 120 then finishes valve trainwork including finishing intake and exhaust seats and guides 28,29.Machine table 101 is then indexed 90 degrees to enable CNC machine 120to finish cam shaft bore 72.

[0030] As shown in FIG. 4, after the second five axis CNC machine 120performs the third machining operation OP-60 on cylinder head 12, thecylinder head is then removed from the second five axis CNC machine andwashed as shown in operations OP-70 block 94. Cylinder head 12 is theninspected and shipped for assembly to cylinder block 14 as shown inoperations OP-80 block 96.

[0031] While embodiments of the present invention have been illustratedand described, it is not intended that these embodiments illustrate anddescribe all possible forms of the present invention. Rather, the wordsused in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the present invention.

What is claimed is:
 1. A method for machining a cylinder headcomprising: loading a cylinder head into a first five axis computernumerically controlled (CNC) machine; locating a first fixture of thefirst CNC machine against a top surface of the cylinder head such thatthe cylinder head is in a horizontal position; machining the cylinderhead in the horizontal position with the first CNC machine; locating asecond fixture of the first CNC machine against a bottom surface of thecylinder head such that the cylinder head is in a vertical position;machining the cylinder head in the vertical position with the first CNCmachine; moving the cylinder head into a second five axis CNC machine;locating a fixture of the second CNC machine against a bottom surface ofthe cylinder head; and machining the cylinder head with the second CNCmachine.
 2. The method of claim 1 wherein locating a first fixture ofthe first CNC machine against a top surface of the cylinder headcomprises: locating the first fixture of the first CNC machine withrespect to cylinder head cast locators and combustion chamber buttons ofthe cylinder head.
 3. The method of claim 1 wherein locating a secondfixture of the first CNC machine against a bottom surface of thecylinder head comprises: locating the second fixture of the first CNCmachine with respect to manufacturing holes of the cylinder head.
 4. Themethod of claim 2 wherein machining the cylinder head in the horizontalposition with the first CNC machine comprises: orienting a spindle ofthe first CNC machine adjacent the bottom surface of the cylinder headto machine the bottom surface of the cylinder head with the spindle as afunction of depth of the combustion chamber buttons of the cylinderhead.
 5. The method of claim 4 wherein machining the cylinder head inthe horizontal position with the first CNC machine further comprises:indexing the cylinder head by 90 degrees; and machining a front sideface of the cylinder head.
 6. The method of claim 5 wherein machiningthe cylinder head in the horizontal position with the first CNC machinefurther comprises: indexing the cylinder head by 180 degrees; andmachining a rear side face of the cylinder head.
 7. The method of claim4 wherein machining the cylinder head in the vertical position with thefirst CNC machine further comprises: orienting a spindle of the secondCNC machine adjacent the top surface of the cylinder head to machine thetop surface of the cylinder head.
 8. The method of claim 1 whereinmachining the cylinder head with the second CNC machine comprises:orienting a spindle of the second CNC machine adjacent the top surfaceof the cylinder head to machine the top surface of the cylinder headwith the spindle.
 9. A system for machining a cylinder head comprising:a first five axis computer numerically controlled (CNC) machine having afirst fixture operable for locating against a top surface of a cylinderhead such that the cylinder head is in a horizontal position to enablethe first CNC machine to machine the cylinder head in the horizontalposition, and a second fixture operable for locating against a bottomsurface of the cylinder head such that the cylinder head is in avertical position to enable the first CNC machine to the cylinder headin the vertical position; and a second five axis CNC machine having afixture operable for locating against a bottom surface of the cylinderhead to enable the second CNC machine to machine the cylinder head. 10.The system of claim 9 wherein: the first fixture of the first CNCmachine is located against a top surface of the cylinder head withrespect to cylinder head cast locators and combustion chamber buttons ofthe cylinder head.
 11. The system of claim 9 wherein: the second fixtureof the first CNC machine is located against a bottom surface of thecylinder head with respect to manufacturing holes of the cylinder head.12. The system of claim 10 wherein: the first CNC machine machines thecylinder head in the horizontal position by orienting a spindle of thefirst CNC machine adjacent the bottom surface of the cylinder head tomachine the bottom surface of the cylinder head with the spindle as afunction of depth of the combustion chamber buttons of the cylinderhead.